1. Field of the Invention
The present invention relates to wells, drilling wells, well operations, to methods, apparatus and products for drilling wells. In another aspect, the present invention relates to wells, cementing wells, and to methods, apparatus and products for cementing wells. In even another aspect, the present invention relates to wells, primary cementing wells, and to methods, apparatus and products for primary cementing wells.
2. Brief Description of the Related Art
In the drilling and completion of an oil or gas well, a cementing composition is often introduced in the well bore for cementing pipe string or casing in a process known as primary cementing. In primary cementing, a cementing composition is pumped into the annular space between the walls of the well bore and the casing. The cementing composition sets in the annular space, supporting and positioning the casing, and forming a substantially impermeable barrier/mass or cement sheath. An essential function of cementing is to prevent fluid exchange between the different formation layers through which the hole passes and to control the ingress of fluid into the well, in particular to limit the ingress of water. In production zones, the casing, the cement and the formation are all perforated over a depth of a few centimeters.
A variety of cementing compositions exist in the art and have been used for primary cementing. Considerations for selecting a cementing composition include relatively short term concerns, such as set times for the cement slurry, as well as functional and long term concerns such as whether a composition is environmentally acceptable, easily mixable, non-settling under static and dynamic conditions, will develop near one hundred percent placement in the annular space, resist fluid influx, and have the desired density, thickening time, set up time, fluid loss, strength development, and zero free water.
A number of patents and patent applications are directed to primary cementing wells, the following of which are only a small few.
U.S. Pat. No. 4,768,593, issued Sep. 6, 1988, to Novak discloses This application discloses a process for drilling and primary cementing a well using a drilling fluid containing a polymeric material which may be cemented into a well cement by irradiation with a suitable radioactive source
U.S. Pat. No. 5,151,203, issued Sep. 29, 1992, to Riley et al., discloses a composition for and method of performing primary cementing operations. The method comprises the use of a water slurry of a thixotropic cementing composition which rapidly develops sufficient static gel strength to reduce if not eliminate annular gas migration.
U.S. Pat. No. 5,327,969, issued Jul. 12, 1994, to Sabins et al., discloses a method of preventing gas migration during primary well cementing. The method basically comprises the steps of displacing a cement slurry into the annulus between a string of pipe to be cemented in a well bore and the walls of the well bore, determining the initial surface pressure in the pipe after the cement slurry is placed in the annulus, displacing additional cement slurry into the annulus as is necessary to make up for losses in the surface pressure due to cement slurry gel strength development and volume reduction whereby the surface pressure is maintained substantially equal to the initial surface pressure until the cement slurry develops a predetermined gel strength sufficient by itself to prevent gas migration, and then allowing the cement slurry to set into a hard impermeable mass in the annulus.
U.S. Pat. No. 5,343,950, issued Sep. 6, 1994 to Hale et al., discloses An extended reach well such as the deviated wells typically drilled from offshore platforms is drilled using a drilling fluid comprising blast furnace slag and water which drilling fluid is circulated during the drilling to lay down a filter cake. Thereafter, an activator is added and generally, an alkaline material and additional blast furnace slag, to produce a cementitious slurry which is passed down a casing and up into an annulus to effect primary cementing.
U.S. Pat. No. 5,343,951, issued Sep. 6, 1994 to Cowan et al., discloses a slim hole well drilled using a drilling fluid comprising blast furnace slag and water which drilling fluid is circulated during the drilling to lay down a filter cake. Thereafter, an activator is added and generally, an alkaline material and additional blast furnace slag, to produce a cementitious slurry which is passed down a casing and up into an annulus to effect primary cementing.
U.S. Pat. No. 5,370,185, issued Dec. 6, 1994 to Cowan et al., a cementitious slurry produced by combining an aqueous drilling fluid with a slurry of Portland cement in oil. Generally the drilling fluid is an aqueous drilling fluid containing clay such as prehydrated bentonite. The resulting composition has a particular utility in primary cementing operations for oil wells.
U.S. Pat. No. 5,829,523, issued Nov. 3, 1998 to Sabins et al., discloses primary well cementing methods and apparatus. The methods basically comprise the steps of releasing a displacement plug into the casing to be cemented and pumping a first displacement fluid behind the displacement plug while measuring the quantity of the first displacement fluid required to land the displacement plug on a float collar or the like connected near the bottom of the casing, releasing a bottom cementing plug into the casing and pumping a cement slurry behind the bottom cementing plug in a predetermined quantity and then releasing a top cementing plug into the casing and pumping a second displacement fluid behind the top cementing plug in a quantity substantially equal to the measured quantity of the first displacement fluid thereby ensuring that the cement slurry is not under or over displaced in the annulus between the casing and the well bore.
U.S. Pat. No. 6,065,539, issued May 23, 2000 to Noik et al., discloses a method of cementing a casing in a well drilled in the ground comprises injecting a liquid material comprising phenol-formol resin from the surface, wherein the resin is modified by means of a determined amount of furfuryl alcohol, and an amount of mineral filler unreactive towards the resin is added. The invention further relates to a thermosetting cementing material comprising phenol-formol resin. The resin is modified by means of an amount of furfuryl alcohol and comprises at least a proportion of an unreactive granular filler.
U.S. Pat. No. 6,626,991, issued Sep. 30, 2003 to Drochon et al., discloses a cement slurry for cementing an oil well or the like, the slurry having a density lying in the range 0.9 g/cm.sup.3 to 1.3 g/cm.sup.3, and being constituted by a solid fraction and a liquid fraction, having porosity (volume ratio of liquid fraction over solid fraction) lying in the range 38% to 50%. The solid fraction is constituted by a mixture of lightweight particles, microcement and optionally portland cement and gypsum. Such cements have remarkable mechanical properties due to their very low porosity in spite of having very low density.
U.S. Pat. No. 6,776,237, issued Aug. 17, 2004 to Dao et al., discloses lightweight cement compositions and methods of cementing a subterranean zone penetrated by a well bore utilizing the compositions are provided. A lightweight cement composition of the invention is basically comprised of a coarse particulate hydraulic cement, an ultrafine particulate hydraulic cement mixture comprised of slag cement and a Portland or equivalent cement, fly ash, fumed silica, hollow glass spheres and water.
U.S. Pat. No. 6,793,730, issued Sep. 21, 2004 to Reddy et al., discloses methods for cementing. The methods are basically comprised of the steps of preparing a cement composition comprised of hydraulic cement, water, gas, surfactants, a cement early strength accelerator and a mildly set retarding cement dispersing agent, placing the cement composition in the annulus between the casing string and the well bore and allowing the cement composition to set into a hard impermeable mass. The cement composition used can alternatively comprise hydraulic cement, a water reducing additive, a dispersing additive, a set accelerating additive and water. Also, the cement composition can be made environmentally benign by using water reducing and dispersing additives, set retarding additives, and compressive strength and set accelerating additives which are environmentally degradable.
U.S. Pat. No. 6,892,814, issued May 17, 2005, to Heathman et al., discloses cement comprising barite, a process for preparing such cement, and methods of cementing in a subterranean formation or well bore using such cement are provided. The cement is prepared by introducing coarse barite to the cement, the course barite comprising particles having a particle size primarily greater than about 125 microns. Preferably, 90 percent of the barite particles is greater than about 125 microns in size. The presence of the coarse barite in the cement causes the cement to have a relatively low viscosity. Introducing the barite to the cement also increases the density of the cement, thus rendering the cement capable of controlling high hydrostatic pressures in a well bore.
In spite of the advances in the prior art, conventional cement systems suffer from a 6 hour safety margin to dump the slurry; long set times; low shear bond values; long cement lengths, and long wait on cement (WOC) times causing high expense.
Thus, there still exists a need in the art for improved methods, apparatus and products for cementing wells.
There also exists a need in the art for improved methods, apparatus and products for primary cementing operations of wells.